1. Field of the Invention
This invention relates to fire resistant (difficultly inflammable) fluids based on esters of phosphoric acid. More particularly, the invention relates to a fire resistant fluid based on a phosphoric acid ester or a mixture of phosphoric acid esters and containing a corrosion and hydrolysis inhibitor.
2. Discussion of the Prior Art
Hydraulic fluids based on phosphoric acid esters have been used for some time. They have characteristics suitable therefor; particularly, they are not easily inflammable, so that they are used above all in systems comprising closed hydraulic circuits such as hydraulic systems of turbines and of pressure casting, continuous casting and press plants. The use of such fluids is described for example in U.S. Pat. No. 3,468,802 and U.S. Pat. No. 3,723,315.
Although such fluids are not easily inflammable and of relatively high thermal stability, they may, in certain applications, possess insufficient resistance to oxidation and/or hydrolysis or they may be highly corrosive to certain metals. To remedy such defects of the known fluids certain inhibitors may be added thereto. For example, certain aminopyridines may be added as antioxidants (U.S. Pat. No. 3,783,132). Also, oxazolines and imidazolines may be added as rust inhibitors (British Pat. No. 1,317,636). Finally, it is known to use certain amino compounds as corrosion inhibitors (U.S. Pat. No. 3,468,802). However, many of the proposed rust inhibitors show undesirable side effects which impair the applicability of the hydraulic fluid.